validation on attributes

hello.
i want to validate additional properties stored in attributes. specially checking for duplicates when creating new row.
is there any method to do that?

Which attributes? Creating where?

for example we have a mobile number for driver stored in attributes because we don't have any corresponding field in driver table. when creating new driver we have to check if mobile number already exist or not

The right thing to do would be to add a new field in the database and have a unique constraint on it.